The present invention relates to the field of video sensing systems and, in particular, to a data transfer system for sensing coded information displayed on scan lines on a video screen.
The transfer of data through a television or a video screen is known. For example, U.S. Pat. No. 4,329,864, issued to Monteath et al., discloses an apparatus using a light sensing system for sensing information displayed in a selected region of scan lines on a light emitting device. In the disclosed apparatus, a light pen utilizes a photo cell to read a region or patch comprised of three or four scan lines sensed as a group to determine if the scan lines in the region are on or off. The Monteath patent assumes a 50 fields per second scanning rate, producing a bit rate of 50 bits per second because the region yields one bit per screen refresh.
U.S Pat. No. 4,613,904, issued to Lurie, discloses an apparatus to read a rolling bar code from a selected location on a television screen. The apparatus disclosed by Lurie is removably secured to the television screen and uses a photo cell to receive successive channel identifying information displayed on the screen. The apparatus in Lurie is directed toward monitoring of television channels and includes a previous-code register to store channel identification words to determine when a viewer has switched channels.
U.S Pat. No. 4,956,639, issued to Uemura, includes a photosensor for reading bar code data and a counter circuit for counting the coded data read by the photosensor to determine whether the data is displayed by an odd-number scanning field or an even-number scanning field and produce a corresponding signal. A plurality of timing circuits interact with the signal to synchronize the storing of the data.
U.S Pat. No. 3,993,861, issued to Baer, discloses a system for communicating a binary-coded, digital message that is displayed as a brightness modulation in a display screen. A light sensor detects the brightness modulation of each scan line to determine if segments of the scan line appear bright or dark, corresponding to digital "ones" and "zeros".
The rolling bar code devices disclosed in the Monteath, et al. and Lurie patents require complex circuitry to receive and analyze sequential information. Also, the speed of the disclosed devices is limited to the refreshment rate of the display screen, as disclosed in Monteath et al., a rate of 50 bits per second. While this speed is sufficient for the programming of a television receiver for later use, as suggested in Monteath et al., or for storing channel identifying information, as proposed by Lurie, a rate of 50 bits per second is insufficient for many "real time" data transfer applications. The apparatus disclosed by Uemura requires complex timing circuitry to determine whether data is being display on an odd or even scanning field. Finally, the Baer apparatus requires the use of an expensive high speed photo transistor to sense multiple on and off conditions occurring within a single scan line.
Musical data, including chord configurations, is used by musicians to determine notes in harmony with a composition. When a musical instrument is played in accompaniment with a musical composition, the correct notes must be selected from a set of notes in the scale of the music. The playing of a note that is not in the set of notes in the scale of the composition results in a dissonant sound. For example, a composition played in the key of C may be easily accompanied by using only the white keys in the C scale on a piano, but using one of the black keys will result in the playing of a dissonant note.
One method of transmitting compositions to musicians is through a television program or a music video. Accompanying a music video with a musical instrument requires selecting notes in the scale of the composition. Problems arise because the chords, melody lines and expression of the composition may change rapidly, resulting in a continuously changing set of notes within the scale of the music. Beginning musicians, in particular, lack the skill to accurately select notes in harmony with a composition. Therefore, it is desirable to provide an inexpensive system for transferring data that is capable of transmitting real-time chord configuration changes by simultaneously transferring multiple bits of composition data.